The present invention relates to a magnetic recording and reproducing method for recording and reproducing digital information and to an apparatus therefor, and more particularly to a magnetic recording and reproducing method suitable for reshaping a waveform by using an automatic equalizer in the reproduction of a digitally recorded signal and to a recording and reproducing apparatus for practising it.
In reproducing a recorded signal in a prior art magnetic recording and reproducing apparatus, particularly a magnetic disk drive, a phase discrimination system has been adopted. For example, in JP-A-57-88511, a reproduced signal waveform is reshaped by two equalizers to attain substantially perfect equalization, and then a pulse corresponding to a peak of the reproduced signal is generated by differentiation so that "1" and "0" are discriminated by the presence or absence of the pulse. In JP-A-57-88511, it is assumed that a zero-crossing point of the differentiated signal does not shift if a shift of a peak point of the reproduced signal waveform is eliminated by the use of a plurality of equalizers.
In JP-A-62-42368, an equalization constant in equalizing a reproduced signal waveform is switched between an inner track and an outer track of a magnetic disk, because degrees of interference which the reproduced signal waveform receives differ between the inner track and the outer track of the magnetic disk due to a difference of a recording density.